Currently, due to the global energy shortage as well as the increasing awareness of environmental protection, electric vehicle batteries and energy storage batteries are popular in the market. In general, high-capacity secondary batteries (nickel-hydrogen batteries, nickel-cadmium batteries, lithium batteries, lead-acid batteries, etc.) in the market are in rectangular shape, which is especially true with respect to nickel-hydrogen batteries. Nickel-hydrogen batteries having a capacity higher than 20 Ah adopt a rectangular shape, as it is difficult to dissipate heat in high-capacity batteries which are prone to thermal runaway. However, rectangular secondary batteries fail to meet market requirements due to inherent defects, while conventional cylindrical secondary batteries need to be improved in terms of high current charge-discharge capability and performance of dissipation of heat from inner parts of batteries. Furthermore, positive and negative plates of existing secondary batteries are solder-connected with lead-out terminals via lugs with soldering points soldering connecting pieces required. When current is large or battery short circuit occurs, the lugs or the connecting pieces are heated to be red-hot, which may cause battery burning or other severe safety accidents.